Astacidea

Freshwater crayfish

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Introduction

Freshwater crayfishes are taxonomically distributed among three families; two Northern Hemisphere families, Astacidae and Cambaridae and one Southern Hemisphere family, Parastacidae. There are two centers of species diversity for freshwater crayfishes. The first is located in the Southeastern United States where some 80% of the cambarid species can be found. The second center of diversity is in Victoria, Australia; housing a large proportion of the parastacid species. Freshwater crayfishes naturally occur on all of the continents except Africa (Figure 1). The Astacidae are distributed West of the Rocky Mountains in the Northwest United States into British Columbia, Canada and in Europe. The Cambaridae are found in the Eastern United States and south through Mexico. The Parastacidae are distributed in Australia, New Zealand, South America, and Madagascar.

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Figure 1. World distributions of the three crayfish families.

Discussion of Phylogenetic Relationships

The phylogenetic relationships among the freshwater crayfish families and their
relationships to lobster-like ancestors has been of considerable debate for at least 100
years. Two alternative hypotheses have been proposed for the origins of crayfishes. The
first supposes a diphyletic origin of astacoids and parastacoids suggesting independent
invasion of the freshwater habitat (Huxley, 1880). This idea is supported by the two
centers of diversity in the northern and southern hemispheres and by a number of
morphological features (Hobbs, 1974). However, Ortmann (1902) argued for a monophyletic
origin of the crayfishes. This position has recently been supported by sperm
ultrastructure characteristics (Jamieson, 1991) and by embryonic characters (Scholtz,
1993). Because of this ongoing debate, the positioning of Parastacidae is shown as
unresolved.

Page: Tree of Life
Astacidea. Freshwater crayfish.
Authored by
Keith A. Crandall and James W. Fetzner, Jr..
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